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Grape grower Mike Sauer is not afraid to experiment on a small scale with different irrigation regimes. Sometimes, the practices work, while other times, he’s abandoned the new ideas.

One that didn’t work was drip irrigation on Concords. Drip is a more efficient system that uses less water than overhead sprinklers—but that experiment was converted back to overhead sprinklers because Sauer couldn’t achieve the tonnage necessary to make production economical.

An experiment that he continues to test in his Red Willow Vineyard at Wapato, Washington, is partial root-zone drying, a technique developed in Australia that alternates drip irrigation on either side of the vine. Data from arid regions of Australia and Spain have shown that it improved water use efficiency and wine grape quality.

Sauer’s trial involves three rows of Lemberger wine grapes situated within a block that follows regulated deficit irrigation, a management practice that limits the total amount of water a vine receives to induce stress for a specified period of time. Regulated deficit irrigation is used to control canopy size and enhance berry characteristics, and is used primarily in red wine grape varieties.

The three Lemberger rows are on the same irrigation schedule as the rest of the block, except that they have two separate drip lines on each side of the vine. The amount of water applied and timing of irrigation is the same in both partial root-zone drying and regulated deficit irrigation. But under the partial root-zone trials, only one side of the vine is watered, with the alternating side watered during the next irrigation cycle.

“It looks like the vine is stressed more under the partial root-zone drying method in comparison to the regulated deficit treatment,” Sauer observed. He also noted that he had a smaller canopy and less vigor in the vines receiving the alternating irrigation.

“The concept behind partial root-zone drying is that you should be getting a larger root-zone compared to root zones grown under a drip line,” he explained. “It may be that I need to go to shorter watering intervals with the partial root-zone method as it may be too much of a deficit.”

He maintains a wide berm under the vine to help separate the area into two distinct irrigation zones.

“I’m going to continue looking at partial root-zone,” he said, but added that he will experiment more with the timing of irrigation in the coming year.